Journal of Elementology
ISSN 1644-2296
Szajnar K., Znamirowska A., Kalicka D., Kuźniar P. 2017. Fortification
of yoghurts with various magnesium compounds. J. Elem., 22(2): 559-568.
DOI: 10.5601/jelem.2016.21.3.1226
ORIGINAL PAPER
FORTIFICATION OF YOGHURTS WITH VARIOUS
MAGNESIUM COMPOUNDS
Katarzyna Szajnar1, Agata Znamirowska1, Dorota Kalicka1,
Piotr Kuźniar2
2
1
Department of Dairy Technology
Department of Food and Agriculture Production Engineering
University of Rzeszow
Abstract
Owing to the presence of B vitamins, proteins and lactose, milk and dairy products fortified with
magnesium could function as transporters of magnesium to the human body. The aim of the
study was to determine the effect of the type of an applied magnesium compound on the dynamics of fermentation, syneresis, texturometric profile and colour of yoghurts. The yoghurts produced were thickened with 3% addition of skimmed milk powder and fortified with various
magnesium compounds in the amount of 30 mg Mg 100 g-1 of milk. The fermentation of milk
was carried out with starter yoghurt cultures at the temperature of 45°C for 4.5 hours. During
the milk fermentation, changes in acidity were examined immediately after the addition of the
starter, after 2 h of incubation and after 4 h of incubation. After 24 h of cold storage, texture,
syneresis, pH, titratable acidity and colour of yoghurts were determined. The magnesium compounds used for the fortification of milk in the dose of 30 mg Mg 100 g-1 of milk did not inhibit
fermentation. After 24 h of storage, all yoghurts fortified with magnesium had a pH typical of
fermented milk. Among the magnesium compounds used, magnesium bisglycinate had the strongest alkalizing impact on acidity of milk prior to fermentation. Fortification of yoghurts with
magnesium compounds reduced syneresis of the whey in yoghurts. The texturometric profile of
yoghurts changed depending on the type of an applied magnesium compound. Comparable components of texture were determined in control yoghurts and in yoghurts enriched with magnesium D-glukonate hydrate. Magnesium L-pidolate and magnesium chloride hexahydrate significantly reduced hardness and adhesiveness of yoghurt curd. Enriching yoghurts with magnesium
bisglycinate, magnesium L-lactate, magnesium chloride hexahydrate, magnesium L-pidolate and
magnesium acetate caused a darker colour compared to the colour of yoghurts which were not
enriched.
Keywords: yoghurt, texture, magnesium, syneresis, colour, fermentation process.
mgr inż. Katarzyna Szajnar, Department of Dairy Technology, University of Rzeszow,
2D Ćwiklińskiej St., 35-601 Rzeszow, Poland, e-mail: [email protected]
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INTRODUCTION
Food enrichment has a significant impact on the health of consumers,
and therefore this process must be carefully planned and consistent with the
state’s nutritional policy. The amount of an enriching substance added to a
food product should be sufficient to achieve the intended health effect but it
must not interfere with the absorption and metabolism of other nutrients or
lead to overdosing (Gahruie et al. 2015).
With the consumption of yoghurts in Poland on the increase, enrichment
of these dairy products can limit or prevent diseases related to deficiency of
minerals. As numerous medical studies show, irrespective of a country, age
or gender, a poor supply of magnesium in human diet causes a major health
threat (Wojtasik et al. 2009, Grzebisz 2011). The average use of magnesium
from a diet by the human body is 40-50%, and its absorption increases in the
presence of B6 vitamin, lactose and protein. Milk has been determined to
contain 0.03-0.06 mg 100 g-1 of B6 vitamin, 4.77% of lactose and 3.48% of
protein (Kozikowski, Przybyłowicz 1994, Wszołek 1997, Król et al. 2011,
Bobrowska-Korczak 2015). Therefore, milk and dairy products fortified with
magnesium could function as transporters of magnesium into the human
body (Ziarno 2004, Gerhart, Schottenheimer 2013, Szeleszczuk, Kuras 2014,
Gahruie et al. 2015). An appropriate magnesium compound should be selected for fortification of dairy products, one that would meet technological,
economic and nutritional expectations. Achieving the desired effect of the
enrichment and production of a food product that satisfies the above requirements is not always possible, which may account for the modest range of
fortified products on the Polish market.
Magnesium from an appropriate source and added to dairy products should be well absorbed by the body, safe in use, have the desired solubility,
chemical and heat stability, should not interact with other components or
cause changes in sensory attributes and shorten the shelf-life of a final products (Lawless et. al. 2003, Regulation (EC) No. 1925/2006).
The aim of the study was to determine the effect of the type of a several
magnesium compound added to yoghurt on the dynamics of fermentation,
syneresis, texturometric profile and colour of yoghurts.
MATERIAL AND METHODS
The experiment was composed of two stages. The first stage included
production of yoghurts (2% fat milk) thickened with 3% of milk powder and
fortified with magnesium compounds 30 mg Mg 100 g-1 of milk: magnesium
acetate pure p.a. (CH3COO)2Mg· 4H2O (Chempur, Poland), magnesium L-pidolate C10H12N2MgO6 (Sigma, France), magnesium chloride hexahydrate pure
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p.a. MgCl 2·  6H 2O (Chempur, Poland), magnesium L-lactate hydrate
C 6H 10MgO 6· H 2O (Sigma – Aldrich, Spain), magnesium bisglycinade
MgC4H4O5· 3H2O (Sigma – Aldrich, USA), magnesium D-gluconate hydrate
C12H22MgO· H2O (Sigma – Aldrich, USA), and pasteurized at the temp. of
72°C for 15 seconds. To be in line with Commission Regulation (EC) No
1662/2006 of 6 November 2006 amending Regulation (EC) No 853/2004 of the
European Parliament and of the Council laying down specific hygiene rules
for food of animal, the temperature used during research was 72°C. Magnesium compounds increase the risk of denaturisation of milk proteins at high
temperature, and the choice of the above pasteurization temperature not
only minimized the denaturisation process, but it also helped us to avoid
using different pasteurization temperatures for various magnesium compounds (Ziarno et al. 2009). The established amount of magnesium did not
cause thermal denaturation of proteins of milk during its pasteurization (at
the temp. of 72°C for 15 s). The fermentation with the use of the yoghurt
starter culture YC-X16 (Chr. Hansen) was performed at 45°C for 4.5 h and
then fermented beverages were cooled down to 5°C. The beverages were examined during incubation for the change of yoghurt’s acidity directly after
addition of the starter, after 2 h and also after 4 h of incubation. In the second stage of the study, after 24 hours of cold storage (at 5°C), yoghurts were
analyzed for syneresis, to which end a sample of yoghurt weighing 25 g was
placed on a paper filter in a funnel. The funnel was placed in a measuring
cylinder (of known weight) and was left for 120 min at 5°C. Whey leakage
(the quantity of whey) was weighed and the percentage was calculated in
relation to the weight of the sample (Cueva, Aryana 2008). The pH determination was performed with the electrometric method by measuring the activity of hydrogen ions with a pHmeter Mettler Toledo FiveEasy (Switzerland).
Potential acidity was established by titration of 0.25N samples with standard solution of sodium hydroxide in the presence of phenolphthalein as an
indicator. Texture was assessed with an analyzer Brookfield CT3 (USA)
equipped with Brookfield Texture Pro CT software. For determination, the
TPA (Cycle Count 2) was selected with a sample of solid state yoghurt put
without mixing in a 100 ml container, at the following settings: sample – cylinder 66.00 mm x 33.86 mm, force 0.1 N, head speed 1 mm s-1, table TA-BTKIT, probe TA3/100 (acrylic cylinder 35 mm length). Colour was analyzed by
a A. Minolta chromameter CR-400. A microcolour tristimulus colorimeter
(Konica Minolta Sensing Inc., Milton Keynes, UK) was used for the determination of L*, a*, and b* values.
The experiment was repeated three times and each parameter was measured five times. The mean and standard deviation were calculated from the
results using the software Statistica 12.0 (StatSoft, USA). The univariate
analysis of variance was applied to evaluate the influence of the type of a
magnesium compound used on the properties of fermented milk beverage.
Significance of differences between the averages (p ≤ 0.05) was estimated
with the Tukey’s test.
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RESULTS AND DISCUSSION
Among the extensive literature on fermented dairy products there are
few works describing changes in acidity during fermentation of milk beverages fortified with mineral compounds. However, as it is known, the presence
of metals such as Cu, Zn, Cd, Pb and Hg in milk may cause changes in the
fermenting activity of dairy bacteria, resulting in either a stimulatory or an
inhibitory effect on fermentation (Ocak, Köse 2010). The type of magnesium
compounds applied for enriching milk (30 mg Mg 100 g-1 of milk) had a significant impact on pH and titratable acidity of milk during fermentation. The
highest pH directly after the addition of starter was determined in milk fortified with magnesium bisglycinate (pH = 7.01), and this value was statistically significantly higher than in other samples. The lowest value of pH was
obtained in milk enriched with magnesium acetate and magnesium chloride
(pH = 6.24), but it was not significantly different from the pH of the control
milk. High pH obtained after the addition of magnesium amino acid chelate
results from alkalizing properties of this compound (Hartle 2006). When
controlling pH after two hours of fermentation, the smallest decrease in the
value of pH compared to the control milk was found in milks enriched with
magnesium bisglycinate and magnesium acetate. The differences turned out
to be statistically significant. After 2 h of fermentation, the pH closest that
of the control milk was found in milk with the addition of magnesium chloride.
After four hours of fermentation, significantly higher (p ≤ 0.05) pH than in
the control sample was determined in milks enriched with magnesium acetate,
magnesium L-lactate hydrate, magnesium L-pidolate and magnesium
bisglycinate (Figure 1). However, significantly lower pH compared to the
control sample was found in milk with the addition of magnesium chloride
Fig.1 The effect of the type of a magnesium compound on pH of yoghurts during incubation
process: a, b, c, d – different letters indicate a statistically significant difference between
the magnesium compounds at the same time (p ≤ 0.05)
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hexahydrate. Among all the magnesium compounds used for fortification, the
highest pH was caused by the addition of magnesium acetate during fermentation. In the study by Ocak, Köse (2010) on the effects of fortifying milk
with Cu, Fe and Zn minerals on the production and texture of yoghurt, the
presence of Cu and Zn in milk was found to have had an inhibitory effect on
the fermenting activity of a yoghurt starter culture. The incubation time was
longer in Cu and Zn fortified yoghurt than control yoghurts and the Fe fortified one.
The added magnesium compounds also affected titratable acidity of processed milk compared to the value of acidity of the control milk (Figure 2).
Fig. 2 The effect of the type of a magnesium compound on titratable acidity of yoghurts during
incubation process: a, b, c, d – different letters indicate a statistically significant difference
between the magnesium compounds at the same time (p ≤ 0.05)
Significantly higher titratable acidity of milk after the addition of starter
was determined in milk magnesium acetate compared to the acidity of the
control milk (p ≤ 0.05). The addition of magnesium chloride hexahydrate and
magnesium bisglycinate resulted in a significant decrease in milk’s acidity,
particurally in comparison with the control milk (p ≤ 0.05). After 2 h of fermentation, significantly lower titratable acidity was found in milks with the
addition of magnesium acetate and magnesium L-lactate hydrate in relation
to the control sample (p ≤ 0.05). In contrast, the addition of magnesium chloride hexahydrate and magnesium D-gluconate hydrate did not significantly
change the acidity of milk in the second hour of fermentation (p ≤ 0.05).
At the end of the fermentation process, significantly higher acidity was obtained in milks enriched with magnesium D-gluconate hydrate compared to the
rest of milks (p ≤ 0.05). Compared to the control sample, significantly lower
titratable acidity was determined in milks enriched with magnesium acetate
and magnesium chloride (p ≤ 0.05).
The value of pH after 24 h of cold storage was reduced in all analyzed
yoghurts (Table. 1). Significantly higher pH was obtained in yoghurts enriched with magnesium acetate and magnesium L-lactate hydrate than in
14.52 ± 0.22
b*
14.50 ± 0.07
-4.020 ± 0.05a
96.92 ± 0.49b
41,85 ± 3.16ab
36.00 ± 0.00b
4.475 ± 0.02a
Magnesium
L-pidolate
14.54 ± 0.31
-4.113 ± 0.05ab
94.38 ± 0.79a
41,01 ± 0.36a
36,60 ± 0.28b
4.450 ± 0.01a
Magnesium
chloride
hexahydrate
14.58 ± 0.22
-4.080 ± 0.04a
98.57 ± 0.87c
44,23 ± 1.68b
36,20 ± 0.01b
4.530 ± 0.00b
Magnesium
L-lactate
14.51 ± 0.19
-4.043 ± 0.17a
96.42 ± 0.56b
44,44 ± 1.02b
37,20 ± 0.28ab
4.495 ± 0.02ab
Magnesium
bisglycinate
2.831 ± 0.36a
13.50 ± 0.14a
Adhesiveness (mJ)
Springiness (mm)
13.71 ± 0.63a
0.200 ± 0.00b
0.891 ± 0.06b
Magnesium
L-pidolate
13.45 ± 0.73a
0.354 ± 0.15b
0.933 ± 0.21b
Magnesium
chloride
hexahydrate
11.53 ± 0.58b
3.933 ± 1.78a
2.690 ± 0.04c
Magnesium
L-lactate
13.28 ± 1.58a
5.733 ± 1.96c
2.217 ± 0.54c
Magnesium
bisglycinate
Explanatory notes:
Table shows mean values and standard deviation.
a, b, c – mean values denoted with different letters within lines differ statistically significantly (p ≤ 0.05)
1.258 ± 0.08a
Magnesiumacetate
Hardness (N)
Properties
14.44 ± 0.43
-3.968 ± 0.09a
97.47 ± 1.62bc
42,38 ± 0.63ab
40,80 ± 0.20c
4.465 ± 0.02a
Magnesium
D-gluconatehydrate
12.85 ± 0.70a
9.133 ± 1.07d
3.060 ± 0.09d
Magnesium
D-gluconatehydrate
The effect of the type of a magnesium compound on texture of yoghurts after 24 h of cold storage
Explanatory notes:
Table shows mean values and standard deviation.
a, b, c - mean values denoted with different letters within lines differ statistically significantly (p ≤ 0.05)
-4.020 ± 0.10a
43,93 ± 1.51ab
Syneresis (%)
a*
35.60 ± 0.00a
Titratable
acidity (ºSH)
95.33 ± 0.78a
4.540 ± 0.04b
pH
L*
Magnesium
acetate
Colour
Properties
12.82 ± 0.71a
7.933 ± 1.35dc
3.113 ± 0.037d
Control
Table 2
14.71 ± 0.35
-4.235 ± 0.13b
98.23 ± 1.95c
44,48 ± 1.33b
35,60 ± 0.10a
4.460 ± 0.01a
Control
Table 1
The effect of the type of a magnesium compound on pH, titratable acidity (°SH), syneresis (%) and colour of yoghurts after 24 h of cold storage
564
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the remaining ones (p ≤ 0.05). In the study by Pirkul et al. (1997), fortification of yoghurt with calcium L-lactate or calcium D-gluconate had statistically significant influence on titratable acidity and pH of yoghurt (p ≤ 0.05).
However, there were no statistically significant differences between the acidity values of the control yoghurt and the yoghurts fortified with a mixture
consisting of both compounds of calcium: calcium L-lactate combined with
calcium D-gluconate.
After 24 h, titratable acidity of yoghurts containing L-pidolate, chloride
hexahydrate, L-lactate hydrate, and D-gluconate hydrate was significantly
higher compared to the acidity determined in the control yoghurts (p ≤ 0.05).
Fortification of milk with magnesium compounds in the amount of 30 mg
Mg 100 g-1 of milk caused a decrease in syneresis by 3.47% in yoghurts with
magnesium chloride hexahydrate, by 2.63% in yoghurts with magnesium
L-pidolate and by 2.10% in yoghurts with magnesium D-gluconate hydrate as
compared to the control yoghurts. In contrast, the addition of magnesium
bisglycinate and magnesium L-lactate hydrate did not impair syneresis. In
the experiment by Achanta et al. (2007), enrichment of yoghurt with 420 mg
Mg 170 g-1 in the form of magnesium carbonate also lead to reduced syneresis in comparison with the control yoghurt, as did the other compounds tested in the cited work, i.e. zinc gluconate, manganese sulfate monohydrate,
sodium molybdate dihydrate, chromium chloride and sodium selenite. According to several authors, syneresis may be limited by increasing the amount
of protein and total dry matter in yoghurts (Bhullar et al. 2002, Martin-Diana et al. 2004, Amatayakul et al. 2006, Akalm et al. 2008). Martin-Diana
et al. (2004) explained this decrease in syneresis by the water retention
capacity of proteins, which increases with the denaturation caused by heat
treatment.
Adding 30 mg Mg 100 g-1 of milk in the form of acetate, L-pidolate, chloride hexahydrate and bisglycinate prior to fermentation caused some darkening of the colour of yoghurts compared to the control yoghurt, as evidenced
by the values L* coefficient (Table 1). In contrast, the addition of magnesium
L-lactate hydrate and magnesium D-gluconate hydrate did not affect significantly the brightness of the colour of yoghurts. The values of parameters a*
and b* indicate a colour shift in space toward green and yellow colours. All
yoghurts fortified with magnesium were characterized by a lower portion of
green and yellow colours than the control yoghurts. Achanta et al. (2007),
examining fat free plain set yoghurts fortified with various minerals, found
that the mean L* values of yoghurts fortified with chromium, magnesium,
manganese and molybdenum were higher than the control. In turn Clowley
et al. (2014), in their research on fortification of reconstituted skim milk powder with different calcium salts, emphasize that the used calcium compounds do not significantly affect the colour brightness. Only fortification with
calcium hydroxide – Ca(OH)2 significantly contributed to a lower intensity of
yellow colour in the tested yoghurt.
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Individual distinguishing features of the texture of yoghurts (Table 2) were
found to depend on the type of a magnesium compound used for enrichment.
The highest adhesiveness was in the yoghurt with the addition of D-gluconate
hydrate, and the highest elasticity was determined in the yoghurt enriched with
L-pidolate. In addition, fortification of milk with magnesium definitely reduced
hardness of yoghurts, where the lowest value of hardness of clot was caused by
the addition of L-pidolate and magnesium chloride hexahydrate, especially in
comparison with the yoghurts without enrichment. In the case of L-pidolate and
magnesium chloride hexahydrate, they were also found to have resulted in the
lowest adhesiveness of yoghurt curds. The texturometric profile most similar to
the control yoghurt was determined in yoghurt with the addition of magnesium
D-gluconate hydrate. Ocak and Köse (2010), examining the texture of yoghurt
with Cu, Fe and Zn minerals, found that Cu addition of 0.2 mg l-1 to yoghurt
caused significantly (p ≤ 0.01) higher firmness and cohesiveness of the product,
while the firmness and cohesiveness values for 3.5 mg l-1 addition of Zn were
significantly lower than those connected with the other doses and metals
(p ≤ 0.05, p ≤ 0.01). In order to increase the firmness of yoghurts enriched with
magnesium, hydrocolloids or whey protein isolate (WPI) may be used; optionally
prebiotics can be added (Guvenet al. 2005, Gustaw et al. 2007, 2011).
CONCLUSIONS
1. The magnesium compounds used for fortification of milk (magnesium
acetate, magnesium L-pidolate, magnesium chloride hexahudrate, magnesium L-lactate hydrate, magnesium bisglycinate, magnesium D-glukonate
hydrate) at a dose of 30 mg Mg 100 g-1 of milk did not inhibit the fermentation process. After 24 h of storage, all yoghurts fortified with magnesium had
pH typical of fermented milks.
2. Among the applied magnesium compounds, the greatest impact on
acidity of milk prior to fermentation was shown by magnesium bisglycinate
acting alkalization.
4. Fortification of yoghurts with magnesium compounds caused reduced
syneresis of whey in yoghurts.
5. Depending on the type of the applied magnesium compound, the
texturometric profile of yoghurts changed. Comparable components of texture
were determined in control yoghurts and in yoghurts enriched with magnesium D-glukonate hydrate. Magnesium L-pidolate and magnesium chloride
hexahydrate significantly reduced hardness and adhesiveness of yoghurt clot.
6. Enrichment of yoghurts with magnesium bisglycinate, magnesium
L-lactate hydrate, magnesium chloride hexahydrate, magnesium L-pidolate
and magnesium acetate caused some darkening of the colour in comparison
with the colour of yoghurts which were not enriched.
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7. D-gluconate magnesium, out of all the examined magnesium substances, seems to be the most preferred form of Mg for yoghurt supplementation
because of the least influence on yoghurt’s texture.
REFERENCES
Achanta K., Aryana K.J., Boeneke Ch.A. 2007. Fat free set yogurts fortified with various minerals. LWT, 40: 424-429.
Akalm A.S., Ünal G., GoncS., Fenderya S. 2008. Effects of whey protein concentrate and fructooligosaccharide on the rheological andsensory properties of reduced-fat probiotic yoghurt.
Milchwissenschaft, 63: 171-174.
Amatayakul T., Sherkat F., Shah N.P. 2006. Physical characteristics of set yoghurt made with
altered casein to whey protein ratios and EPS-producing starter cultures at 9 and 14% total
solids. Food Hydrocolloid, 20: 314-324.
Bhullar Y.S., Uddin M.A., Shah N.P. 2002. Effects of ingredients supplementation on textural
characteristics and microstructure of yoghurt. Milchwissenschaft, 57: 328-332.
Bobrowska-Korczak B., Skrajnowska D., Baran M., Tokarz A., Olędzka R. 2015. Determination
of B-vitamins in milk. Bromat. Chem. Toksykol., 48(3): 254-257.
Clowley S.V., Kelly A.L., O’Mahony J.A. 2014. Fortification of reconstituted skim milk powder
with different calcium salts: Impact of physicochemical changes on stability to processing.
Int. J. Dairy Tech., 67(4): 474-482.
Commission Regulation (EC) No 1662/2006 of 6 November 2006 amending Regulation (EC) No
853/2004 of the European Parliament and of the Council laying down specific hygiene rules
for food of animal origin.
Cueva O., Aryana K.J. 2008. Quality attributes of a heart healthy yogurt. LWT, 41: 537-544.
Gahruie H.H., Eskandari M.H, Mesbahi G., Hanifpour M.A. 2015. Scientific and technical aspect
of yogurt fortification: A review. Food Sci. Hum. Wellness, 4: 1-8.
Gerhart M., Schottenheimer M. 2013. Mineral fortification in dairy. Wellness Foods Europe,
Nuremberg, Germany, 1: 30-36.
Grzebisz W. 2011. Magnesium – food and human health. J. Elem., 16(2): 299-323. DOI:
10.5601/jelem.2011.16.2.13
Gustaw W., Kordowska-Wiater M., Kozioł J. 2011. The influence of selected prebiotics on the
growth of lactic acid bacteria for bio-yoghurt production. Acta Sci. Pol. Technol. Aliment.,
10(4): 455-466.
Gustaw W., Nastaj M., Sołowiej B. 2007. The effect of hydrocolloids addition on rheological
properties of set yoghurt. ŻNTJ, 5(54): 274-282.
Guven M., Yasar K., Karaca O.B., Hayaloglu A.A. 2005. The effect of inulinaz a fat replacer on
the quality of set-type low-fat yogurt manufacture. Int. J. Dairy Tech., 58(3): 180-184.
Hartle J., Ashmead S.D. 2006. Bonds important for amino acid chelates. Feedstuffs, 78(37): 1-3.
Kozikowski W., Przybyłowicz K. 1994. Nutritional value of the cow’s milk components. Prz.
Mlecz., 10: 256-261.
Król J., Brodziak A., Litwińczuk A. 2011. Basic chemical composition and content of selected
whey proteins in milk from different cow breeds and in rennet whey. ŻNTJ, 4(77), 74-83.
Lawless H.T., Rapacki F., Horne J., Hayes A. 2003.The taste of calcium and magnesium salts
and anionic modifications. Food Qual. Prefer., 14(4): 319-325. DOI: 10.1016/S0950-3293(02)00128-3
Martin-Diana A.B., Janer C., Pelàez C.,Requena T. 2004. Effect of milk fat replacement by polyunsaturated fatty acids on the microbiological, rheological and sensorial properties of fermented milks. J. Sci. Food Agr., 84: 1599-1605.
568
Ocak E., Köse S. 2010. The effects of fortifying milk Cu, Fe and Zn minerals on the production
and texture of yoghurt. J. Sci. Food Agr., 8(2): 122-125.
Pirkul T., Erdem Y. K., Temiz A.,1997. Fortification of yoghurt with calcium salts and its effect
on starter microorganisms and yoghurt quality. Int. Dairy J., 7(8-9): 547-552. DOI: 1016/
S0958-6946(97)00030-7
Regulation (Ec) No 1925/2006 of the European Parliament and of the Council of 20 December
2006 on the addition of vitamins and minerals and of certain other substances to foods.
Szeleszczuk Ł., Kuras M. 2014. The importance of calcium in the human metabolism and factors affecting the bioavailability of dietary Biul. Wydz. Farm. WUM, 3: 16-22.
Wojtasik A., Kunachowicz H., Socha J. 2009. Magnesium and needs of their use in healthy children and children of celiac diseae. ŻNTJ, 4(65): 295 -302.
Wszołek M. 1997. Nutritional value, physicochemical and biological properties of goat’s milk
components. Nowa Med., 9: 41-48.
Ziarno M. 2004. Enrichment of dairy products in magnesium. Przem. Spoż., 12: 38-41.
Ziarno M., Zaręba D., Piskorz J. 2009. Fortifying buttermilk with calcium, magnesium, and
whey protein. ŻNTJ, 2(63): 14-27.